void Partition(ElemSet* a, int n)
{
	int left = 0;
	int right = n - 1;
	
	while(left < right)
	{
		while(left < right && a[left] < 0)
		{
			left++;
		}
		while(left < right && a[right] >= 0)
		{
			right++;
		}
		
		if(left < right)
		{
			ElemSet temp = a[left];
            a[left] = a[right];
            a[right] = temp;
            left++;
            right--;
		}
	} 
}